The Future of Multimessenger Astronomy with Neutrinos at the South Pole IceCube and Future Observatories in the Ice Kael Hanson Director, Wisconsin IceCube Particle Astrophysics Center (WIPAC) University of Wisconsin – Madison 12th Latin American Symposium on High Energy Physics November 29, 2018 Classical Astronomy - The Visible Sky

2018 | 11 | 29 K. Hanson - XII SILAFAE 2 The Sky In Gamma Rays

2018 | 11 | 29 K. Hanson - XII SILAFAE 3 The Photon Sky at Ultrahigh Energies

No – this is not me forgetting to add the slide content. Above several hundred trillion eV, photons don’t travel more than galactic distances.

2018 | 11 | 29 K. Hanson - XII SILAFAE 4 M87 – A Nearby Natural Particle Accelerator

2018 | 11 | 29 K. Hanson - XII SILAFAE 5 The Case for Multimessenger Astronomy Take all you are given

High energy astrophysical acceleration sites are likely emitters of gammas, charged ions, and neutrinos. Each particle used as a messenger particle has it own strengths and weaknesses – we can push our knowledge deeper by combining them. Gamma rays: point back to sources and easily detectible but there is problem of interactions in dense sources or in transit over not-so-long distances. PeV and above constrained to intergalactic-scale distances. EM and hadronic production possible and often difficult to discriminate. Cosmic rays: and up to 1019 eV travel over cosmological distances. Not impossible but difficult to trace back to source due to deflection in GMF/IGMF. UHE detection requires large ground arrays.

Neutrinos: point back to sources and offer pristine look even deep into compact objects; no horizon – a good thing overall but has implications in point-source searches; require large, expensive underground or underwater (ice) detector facilities; radio is however promising economical technique at UHE.

2018 | 11 | 29 K. Hanson - XII SILAFAE 6 Challenge / Opportunity: Cosmic Horizons

Neutrinos are alone the only astronomical messengers capable of directly imaging the extreme energy sky. Photons interact with EBL and already at 100’s of TeV are limited to Mpc scales.

Charged cosmic rays processed by galactic and inter-galactic magnetic fields as well as galactic diffusion: energy and angles at observation no longer follow source.

2018 | 11 | 29 K. Hanson - XII SILAFAE Slide 7 Atmospheric Neutrino “Backgrounds”

Neutrinos are also produced in quantity by cosmic ray interactions in the Earth’s atmosphere: decaying mesons yield muons, ne, and nm (not nt however). These form a nearly irreducible background for astrophysical neutrinos (IceCube detects 1 every 5 minutes vs 1/week for astrophysical n).

The handle is the energy: because mesons lose energy in the atmosphere the flux of atmospheric neutrinos is approx. power law with spectral index -3.7.

2018 | 11 | 29 K. Hanson - XII SILAFAE 8 IceCube Still the biggest TeV neutrino telescope The IceCube Collaboration includes > 300 researchers from 47 institutes in 12 countries.

IceCube is one of the NSF’s large facilities (LIGO, LSST, … 2 dozen others).

The Operations and Management of the facility is handled by WIPAC at UW- Madison. In addition to having a large science group, our center supports the technical aspects: computing, data storage, detector maintenance, … The IceCube Neutrino Observatory

IceCube construction began in 2002 with design and procurement of the drill. The first string to be deployed was in Jan 2005. Over the next 6 season 85 more strings were deployed with the last string being “tied off” on December 17, 2010. Full 86 string data taking started May 2011.

TPC: $279M USD - $40M non-US

The South Pole site was chosen (A) Because there is a lot of ice; (B) Logistic support: 5 million lbs. of cargo were delivered and 77 person-years of effort on-ice it took to make IceCube. Everything was at that time airlifted inside LC-130 Hercules aircraft.

2018 | 11 | 29 K. Hanson - XII SILAFAE 12 The IceCube Digital Optical Module (DOM)

Penetrator HV Divider Optical Communicatons / Timing LED Flasher . Large Area Photocathode 10” 10- . Comunications is digital at rate of Board stage Hamamatsu R7081-02 PMT 1 Mbit/s shared by 2 DOMs on a DOM single copper pair. Mainboard (QE 24% @ 420 nm); High QE . The DOMs each timestamp PMT variant (QE 35% @ 420 nm) used in pulses using a local XO. DeepCore DOMs Mu-metal Nevertheless, 1 ns time resolution grid . Low noise 500 Hz bkg count rate in- is achieved through automatic ice @ 0.25 pe threshold. clock synchronization protocol . Glass / Gel 0.5” thick Benthos Delay Board pressure housing rated to 10,000 Digitizer psi. Better transmission in 330 - 400 nm relative to AMANDA OM. IceCube adopted waveform readout Low radioactivity glass. of PMT pulses to deal with complex . Optical calibration Each DOM scattering of photons in ice. There calibrated ε(λ, T) in the lab to about are two digitizers: PMT RTV . 300 MSPS ASIC 14-bit effective gel 7%; in-situ flashers additionally permit in-ice optical measurements resolution but limited to ~500 ns Glass Pressure Housing . 40 MSPS pipelined ADC capture to 6.4 µs

FPGA + ARM CPU SoC. 4k-hit deep Power supplied by 18 AWG Cu pair to surface (3.5 km). 96 V, memory buffer stores hits until readout Smart Sensor Power 3.75 W per channel (DOM) over 1 Mbit digital link to surface.

2018 | 11 | 29 K. Hanson - XII SILAFAE 13 Hot Water Drilling

• 5 MW Drill power plant gives 195°F hot water in closed loop system. • 5500 gallons AN-8 jet fuel / hole • 30 man crew • 30 h drilling – 3 day cycle time • “Hole lifetime” – 24hr • DOM installation – 8 hr • Typical freezeback times > weeks • DOMs not operated in liquid under normal circumstances.

Drilling improved over time. The first 2004-2005 hole took weeks to drill. A few years later the drill crew was able to get the time down to 50 h. By the end – 30 h was achieved with repeatable performance.

2018 | 11 | 29 K. Hanson - XII SILAFAE 14 Detecting Neutrinos in the Ice

IceCube is “water” Cherenkov detector: we detect the charged ultrarelativistic secondaries which are produced in neutrino scattering in ice or detect CR muons and their stochastic secondaries.

Ice is a good calorimetric medium: we can get 10% resolution on E (dE/dX for muons).

Scattering and non-uniformity is problematic both for precision reconstruction and for simulation of the detector. Still we are able to obtain O(½) degree angular resolution for tracks.

2018 | 11 | 29 K. Hanson - XII SILAFAE 15 Ice

The complex ice structure deposited over 100 k-yr contains much structure and is prominent challenge for IceCube: • Simulation of 1010 photons or more for high energy events now possible with GPU acceleration • Not only is there z structure, there is tilt and directional anisotropy!

Ice properties measured with in-ice calibration sources: • 12 high brightness 400 nm LEDs per DOM – a few DOMs have different colors; • Handful of special calibrated sources; • Dedicated dust logging of boreholes – IceCube also contains a few glaciologists.

2018 | 11 | 29 K. Hanson - XII SILAFAE 18 It started with 2 muppets: Bert and Ernie

Quite by accident, while looking for extremely high energy neutrinos from the GZK interacting protons, we found two events in the first year of full IC86 data that didn’t look like any background: they were clear cascade-like events which started inside the detector just like a neutrino should. And they had extremely high energy: 1.05 PeV and 1.15 PeV, each had nearly 100,000 detected photo-electrons!

Now that we had seen real, unmistakable signal events with our “eyes”, we knew how to proceeed:

2018 | 11 | 29 K. Hanson - XII SILAFAE 19 High-Energy Starting Event (HESE) Analysis

Strategy: focus on high-energy events (2 > PeV events in 1 year, either we got really lucky or the ice is full of them). The very simple cut developed (it is now running in real time at Pole) is this: • Qtot > 6000 p.e. : this will setup an energy threshold of approx. 30 TeV, but, again, there should be many events out there based on the two observations; • Use part of IceCube’s outer shell as a veto. It’s OK if hits occur in the veto as the particle exits (PC muons will do this) but not OK if the first hits occur in the veto region. • It is also possible to use data to check the veto performance

The HESE analysis was then sensitive to all flavors above about 60 TeV (muons are penalized slightly because some energy escapes); background could be estimated from data. The effective volume of the search was 400 Mton – about 40% efficient.

2018 | 11 | 29 K. Hanson - XII SILAFAE 20 HESE 6-year Results

2018 | 11 | 29 K. Hanson - XII SILAFAE 21 TXS 0506+056 First Observation of Astrophysical Source in EM and Neutrinos

I've seen things you people wouldn't believe. Attack ships on fire off the shoulder of Orion. I watched C-beams glitter in the dark near the Tannhäuser Gate. All those moments will be lost in time, like tears in rain …

-- Roy Batty (Rutger Hauer) Blade Runner (1982) The IceCube Realtime System

• IceCube operates largest data center on continent • Digital data packets from sensors sent to surface and processed by software trigger and readout system (IceCube DAQ) – 3 kHz trigger rate (mostly cosmic ray muons from above) yields about 10 MB/sec written to disk with ~ 5 sec latency. • Online compute farm performs event reconstructions. • High significance events sent via Iridium satellite link to Northern Hemisphere where automated GCN alerts sent out. • IceCube has been sending RT alerts several years but high- energy tracks sent only since Spring 2016 – about 10/yr. • On 22 Sept 2017 at 20:54:30.43 UTC alert IC170922 issued • 43 seconds elapsed between event in ice and GCN alert dissemination on network.

2018 | 11 | 29 K. Hanson - XII SILAFAE 23 The IceCube HE Muon Event

Event was high energy through-going muon event: ~25 TeV energy deposited in detector with most probable neutrino energy ~ 300 TeV.

Muon track reconstruction to within 0.1° of TXS 0506.

2018 | 11 | 29 K. Hanson - XII SILAFAE 24 Realtime HE Neutrino Candidate IC170922

2018 | 11 | 29 K. Hanson - XII SILAFAE 25 2018 | 11 | 29 K. Hanson - XII SILAFAE 26 “Multimessenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A,” The IceCube, Fermi-LAT, MAGIC, AGILE, ASAS-SN, HAWC, H.E.S.S, INTEGRAL, Kanata, Kiso, Kapteyn, Liverpool telescope, Subaru, Swift/NuSTAR, VERITAS, and VLA/17B-403 teams, Science 361, eaat1378 (2018).

“Neutrino emission from the direction of the blazar TXS 0506+056 prior to the IceCube-170922A alert,” IceCube Collaboration: M.G. Aartsen et al. Science 361, 147-151 (2018).

“The blazar TXS 0506+056 associated with a high-energy neutrino: insights into extragalactic jets and cosmic ray acceleration,” The MAGIC Collaboration: M. L. Ahnen et al, Accepted for publication in The Astrophysical Journal Letters.

“Dissecting the region around IceCube-170922A: the blazar TXS 0506+056 as the first cosmic neutrino source,” P. Padovani, P. Giommi, E. Resconi, T. Glauch, B. Arsioli, N. Sahakyan, and M. Huber, Accepted for publication in Monthly Notices of the Royal Astronomical Society.

“VERITAS Observations of the BL Lac Object TXS 0506+056,” VERITAS Collaboration: Abeysekara et al. The Astrophysical Journal Letters (2018).

“A Multimessenger Picture of the Flaring Blazar TXS 0506+056: Implications for High-Energy Neutrino Emission and Cosmic Ray Acceleration,” A. Keivani, K. Murase, M. Petropoulou, D. B. Fox, S. B. Cenko, S. Chaty, A. Coleiro, J. J. DeLaunay, S. Dimitrakoudis, P. A. Evans, J. A. Kennea, F. E. Marshall, A. Mastichiadis, J. P. Osborne, M. Santander, A. Tohuvavohu, and C. F. Turley, Submitted to The Astrophysical Journal.

“Search for neutrinos from TXS 0506+056 with the ANTARES telescope,” ANTARES Collaboration: A. Albert et al, Submitted to The Astrophysical Journal Letters.

See https://icecube.wisc.edu/pubs/neutrino_blazar for up-to-date information Multi-messenger Follow-Up Observations

2018 | 11 | 29 K. Hanson - XII SILAFAE 28 IceCube Archival Search – Neutrino “Flare”

• Observations divided into 6 periods of differing run configurations. • One period contains significant excess – 19 events on background of 6. • Gaussian time window centered at 13 Dec 2014 with full width of 110 days. • Spectral index of 2.1. • 3.5 σ rejection of background hypothesis.

2018 | 11 | 29 K. Hanson - XII SILAFAE 29 What is TXS 0506 and What Are Implications?

• Known source in EM – z = 0.3365 (GTC Oct 2017) giving distance of 4 Glyr • Blazar (AGN with jet pointed at observer) • Radio, optical, x-ray, and gamma all indicate blazar was in flaring state for weeks / months leading up to the Sep 2017 neutrino alert. • Source had never been considered as likely source of detectable neutrino flux – without MMA observations its presence in IceCube skymaps overshadowed by hotter spots on sky. • Among 50 brightest gamma ray sources in Fermi-LAT catalog  one of most luminous objects, 10x more luminous than Markarians. • This result consistent with previous IceCube analysis giving upper limit of 27% contribution of AGNs to HE diffuse neutrino flux. • Discrimination of acceleration models at source, see https://arxiv.org/abs/1807.04537, hybrid lepton/hadron + multi-zone.

2018 | 11 | 29 K. Hanson - XII SILAFAE 30 IceCube Upgrade

High Energy Array

Cosmic Ray Array IceCube Gen2 – The Future of Neutrino Astronomy Radio Array

IceCube Gen2 White Paper: arXiv: 1412.5106v2 Conceptual Design

A conceptual drawing of the IceCube Gen2 Facility is shown at right. Specific points of design are likely to evolve quite a bit. However salient points are the multiple sub-detectors spanning energy range of ~ GeV to EeV: • Upgrade: low energy, tau neutrinos, precision calibration of ice; • High Energy Array (HEA) – 100 TeV+ neutrino detector using optical sensors evolved from IceCube • Cosmic Ray Array (CRA) – veto array for HEA as well as exploration of cosmic ray physics • Radio Array (RA) – ARA-like or perhaps much denser array of RF power envelope detectors. Overtakes optical in region 100 PeV+

2018 | 11 | 29 K. Hanson - XII SILAFAE 32

PeV-Scale Neutrinos

2.6 PeV 휈휇. The parent Region above 100 TeV is sweet spot for neutrino astrophysics: neutrino’s energy is in the range 5-10 PeV. • Background-free region for study of • Point sources • Correlation studies • Energy spectra • Gen2/HEA would deliver O(10) events per year above 1 PeV • At PeV scales new phenomena arise which help disentangle flavors providing information on source physics: • Tau double bangs – separated – O(1-2) per year in IceCube Gen2/HEA • Glashow resonance events [arXiv:1108.3163 Battacharya, et al] have pure muon, tau lollipop signatures – discrimination of pp versus p at source. • Recent TXS 0506 source  10x IceCube detect several new blazars (an other source classes or exclude?) per year!

2018 | 11 | 29 K. Hanson - XII SILAFAE 34 PeV neutrinos don’t need dense detector

Take Bert – one of the two original ~ 1 PeV neutrinos found in IceCube data.

Study reconstruction of this event with real sparse detector: IceCube with strings removed to simulate wider spacing. With 20 strings separated by 250 m

Vertex resolution 12 m Angular resolution 30° Energy resolution 10%

2018 | 11 | 29 K. Hanson - XII SILAFAE 35 Gen2 Sensor Designs

• Name of the game is photon Upgrade. Other sensor effective collection area: technologies require more R&D. • Several new sensors under Profit from availability of drill holes consideration for Gen2: D-Egg and to deploy future instrumentation mDOM will be utilized in the Phase I and retire risk early.

2018 | 11 | 29 K. Hanson - XII SILAFAE 36 Radio Detection of Neutrinos

Radio technique high threshold – 10’s of PeV – but 10x more cost effective at UHE.

2018 | 11 | 29 K. Hanson - XII SILAFAE 37 The IceCube Phase I Upgrade Gen2 Phase 1: First Steps

Science goals: (a) Probe unitarity of PMNS matrix 7 strings (US 3 | JP 2 | DE 2) densely populated with next (b) Improve calibration and characterization of generation, high performance photodetectors: ice for improved HE multimessenger • Integrates with existing IceCube: data acquisition, event neutrino astronomy filtering, simulation will require extension; • No significant increase in steady-state operations; • Negligible increase in data rate • +3 kW power (+5% increase relative to IceCube) Proposed project leverages significant effort already invested by US/Non-US IceCube groups to develop instrumentation and infrastructure for next-generation neutrino detector at South Pole.

String Module Modules per Array Spacing Spacing String IceCube 125 m 17 m 60

DeepCore 75 m 7 m 60

Phase 1 20 m 2 m 125

2018 | 11 | 29 K. Hanson - XII SILAFAE 39 Neutrino Mixing

With only 7 but densely instrumented strings …

• Expect 2500 CC+NC tau neutrino events per annum. Statistically measure taus based on energy and angle. • Will exlude no-tau appear w 14 sig after 3 years. • Best constraints on atmospheric mixing parameters (maximal mixing / octant for ATMNU).

2018 | 11 | 29 K. Hanson - XII SILAFAE 40 Improving IceCube Reconstructions

Lack of precision knowledge of ice limits angular reconstructions – in particular bad at high energy where, contrary to expectation, the reconstruction gets worse. Cascade reconstruction (right) at PeV has median ang. res of 15° but would be improved to 3-5° with better ice characterization. This applies to muon reconstructions as well with improvements to 0.1 - 0.2 ° foreseen.

Obvious benefit to MMA is improved source localization: HESE-160427a, a 140 TeV track coincident with Pan- STARRS SN PS16cgx.

Improved flavor ID for tau neutrinos to better constrain source physics. This is currently limited by ice anisotropy Improved calibrations are uncertainty: tau double-pulse harder retroactively applicable to than PeV double bang. 10+ years IceCube archival data!

2018 | 11 | 29 K. Hanson - XII SILAFAE 41 Timeline

• IceCube Upgrade Proposal (nee Phase 1 Upgrade) submitted 2016 receives excellent reviews. Submitted to NSF mid-scale program. • NSF FY19 budget request includes allocation for “Big Ideas” which include multi-messenger astronomy ($30 million) and mid-scale infrastructure ($60 million). • Gen2 scale, O(300) million USD must be MREFC project  multiple years in design phases.

Time IceCube Upgrade Milestone

2019Q1 Preliminary Design Review; drill recon season @ Pole Time Gen2 Milestone

2019 Preparation for final design; long lead procurement 2020 Concept Design Review

2020Q1 Final Design Review 2021 Preliminary Design Review

20/21 Pole Season Drill generators ship to Pole; refurb drill structures @ Pole 2022 Final Design Review; begin production

21/22 Pole Season Firn drilling; drill IV&T 2025-2031 Deployment 120 HEA deep ice strings

22/23 Pole Season Deploy 7 strings

2018 | 11 | 29 K. Hanson - XII SILAFAE 42 Conclusions

• Neutrinos are going to play a key role in MMA from now and through the 2020’s. They allow us to reach into the ultrahigh- energy sky and peer deep into exotic high energy phenomena. TXS 0506 first source identified in neutrinos and EM. • Need next generation instrument to study source physics at TXS and to identify other neutrino souces - but this is still a long way off. New Gen2 facility not likely to be fully operational until ~ 2030. • In the short term, with a modest investment, we can improve our knowledge of the ice and get better multimessenger astronomy from IceCube going forward and going backwards too with Phase I Upgrade.

2018 | 11 | 29 K. Hanson - XII SILAFAE 43 THE END